// editor3
#include<stdio.h>
#include<stdlib.h>
typedef struct node{
    int data;
    struct node *left,*right;
}node;

node *root=NULL;

node *create(int num)
{
    node *newnode=(node*)malloc(sizeof(node));
    newnode->data=num;
    newnode->left=NULL;
    newnode->right=NULL;
    return newnode;
}

node *insert(node *root,int num)
{
    if(root==NULL)
    {
        return create(num);
    }
    else if(num<root->data)
    {
        root->left=insert(root->left,num);
    }
    else if(num>root->data)
    {
        root->right=insert(root->right,num);
    }
    return root;
}

node *leaf(node *root)
{
    if(root!=NULL)
    {
        if(root->left!=NULL)
        {
            root->left=leaf(root->leaf);
        }
        if(root->right!=NULL)
        {
            root->right=leaf(root->right);
        }
        else if(root->right!=NULL && root->left!=NULL)
        {
            printf("%d",root->data);
        }
    }
}
int main()
{
    int size,num;
    scanf("%d,",&size);
    for(int i=0;i<size;i++)
    {
        scanf("%d",&num);
        root=insert(root,num);
        
    }
    leaf(root);
    

}